1. Field of the Invention
The present invention relates to an apparatus for automatically fitting over the end of a wire a water-proofing rubber plug that is to be installed in a terminal accommodating chamber of a connector housing. This invention also relates to a method of supplying the rubber plug from a feeder of the rubber plug fitting apparatus to a rubber plug holding portion, and to a method of fitting the rubber plug reliably.
2. Description of the Related Art
FIGS. 17 and 18 show one example of a conventional rubber plug fitting apparatus (Japanese Patent Publication No. 64-9131). This apparatus includes a clamp 44 for holding a wire 43, a guide 45 for guiding the front part of the wire 43, and a rubber plug holder 48 for holding a rubber plug 46 in a groove 47. The rubber plug 46 is installed in a terminal accommodating chamber of a connector housing not shown to prevent ingress of water into the chamber.
The clamp 44 and the guide 45 have at their front ends a V-shaped recess 49 and a projection 50. A front part 43a of the wire 43 protrudes from the guide 45. The rubber plug holder 48 is formed at its side with the groove 47, in which the rubber plug 46 is installed with one half exposed and protruding. The guide 45 is provided with a cover 51 that guides the protruding side of the rubber plug 46. The rubber plug 46 is supplied from a feeder not shown to the rubber plug holder 48.
The rubber plug holder 48, as shown in FIG. 18, is advanced by an air cylinder not shown to insert the front part of the wire 43 into an inner hole 46a of the rubber plug 46 until the wire protrudes a specified length from the rubber plug 46. The front part 43a of the wire is stripped of insulation in the next process and then crimped with a terminal.
FIGS. 19 and 20 show one example of a rubber plug supply section of the conventional rubber plug fitting apparatus. The following description may not strictly correspond to the above example. The rubber plug supply section 53 is intended to feed rubber plugs 2 to the rubber plug holder. Disposed opposite the front of a feeder 54 is a laterally movable temporary receiver 55, which receives and holds a rubber plug 2 in its groove 56 and is moved laterally to feed the rubber plug 2 sideways of the feeder 54. Then, as shown in FIG. 20, the rubber plug 2 is pushed out of the temporary receiver 55 into a holder 58 by a transfer pin 57. If the temporary receiver 55 is not provided, when the rubber plug 2 is pushed out of the feeder 54, the succeeding rubber plugs 2-1 easily fall blocking the smooth feeding.
FIG. 21 shows the rubber plug holder 58 being moved toward a wire guide 59. In this example, the wire guide 59 can be moved backward along the wire 9. The holder 58 pushes the guide 59 backward to insert the front part 9a of the wire 9 into the rubber plug 2.
FIG. 22 shows an example in which the inner diameter of the groove 60 of the rubber plug holder 58 is set larger than the outer diameter of the rubber plug 2. This is based on the fact that when the wire 9 is inserted into the rubber plug 2 as shown in FIGS. 23A and 23B, the outer diameter of the rubber plug 2 increases from D1 to D2. If the groove diameter is set equal to the rubber plug diameter as in the case of FIG. 21, the wire insertion causes the rubber plug 2 to get stuck to the groove, resulting in the plug being dislocated or shifted.
With the above conventional rubber plug fitting apparatus, however, there is a problem that the sideways feeding by the temporary receiver 55 as shown in FIG. 19 makes the equipment large and complex. Further, when the rubber plug holder 58 is moved toward the wire guide 59 as shown in FIG. 21, any slight deviation of their centers will result in the wire 9 failing to be inserted into the rubber plug 2.
Another problem is that if the diameter D3 of the groove 60 of the rubber plug holder 58 is set larger than the outer diameter D1 of the rubber plug 2 as shown in FIG. 23a, the rubber plug 2 is unstable because of plays in the groove as shown in FIG. 24, so that even if the rubber plug holder 58 and the wire guide 59 are aligned in center, the front end of the wire 9 would abut against the rubber plug 2 and get buckled resulting in an insertion failure, especially when the rubber plug has a large insertion resistance.
Similarly, because the guide 59 is slidable longitudinally of the wire, a clearance is produced between the guide and the wire, which may cause the wire to buckle in an initial phase of the rubber plug fitting process.
Further, because the fitting stroke of the rubber plug 2 is defined by the air cylinder, the apparatus cannot deal with a situation where the fitting stroke is changed when a different kind of rubber plug is used. Even in the same size, the rubber plugs produce different fitting resistances according to the size of wire. This means that because the plug, after fitting, is returned from the set stroke by an amount corresponding to the fitting resistance, the final fitting position of the plug will vary.